Pour point reduction



l l l I l United States Patent G POUR POINT REDUCTION Samuel ClydeVaughn, Berkeley, Calif., assignor to Tide Water Dil Company, acorporation of Delaware No Drawing, Application January 28, 1954 SerialNo. 406,900

7 Claims. (Cl. 252-475) This invention relates to pour depressantmaterials suitable for use in conjunction with hydrocarbon oils. Itfurther relates to the means of manufacturing the aforesaid pourdepressant materials, These materials are particularly adapted asadditives for the reduction of the pour-point of gas oils, especiallythose intended for use as fuels for diesel engines, though other oilsmay be treated therewith.

Briefly, the invention comprises reacting urea or thiourea withhydrogenated castor oil at elevated temperatures, cooling the reactionproduct and adding an effective amount thereof to the hydrocarbon oil.Depending upon the amount of reaction product used, the pour-point ofthe treated oil may be reduced 40 or more Fahrenheit degrees below thatof the original oil. The exact mechanism of the pour-point reduction isnot completely known or understood at the present time.

Hydrogenated castor oil suitable for the practice of the inventionconsists primarily of glyceryl-lZ-hydroxystearate, although thecommercial grades often contain minor quantifies of impurities. Whilethe invention contemplates the use of the commercial product, grades ofgreater purity may be satisfactory. A commercial grade of hydrogenatedcastor oil having the following specification is suitable in the presentinvention:

Specific gravity, 70 F, 0.98 to 1.00 Melting point (ASTM D8722), F 183to 188 Acid number 2.0 Ash, percent Below 0.005 Iodine number 3 to 6Saponification number 175 to 185 The urea (or, thiourea) suitable forreacting with hydrogenated castor oil may be that material availablecommercially, though containing minor quantities of impurities, or maybe the pure compound.

In the operation in cold climates of diesel engines using hydrocarbonfuels having boiling ranges between approximately 350 F. and 700 F.difficulties are encountered with many otherwise satisfactory :fuels dueto the precipitation of wax from the oil at low temperatures. Theprecipitated wax at times causes plugging of the fuel lines and evenprevents flow of oil from the fuel tank. Since the more parafiinic typesof gas oils are preferred for diesel engine fuels because of theirbetter combustion characteristics, as indicated by high cetane numbers,and since the more paraflinic oils have the greater tendency toprecipitate wax, the situation is of major importance in the manufactureof quality diesel fuels. Similar troubles, however, are encountered infurnace oils, and the like, as well as with other oils. Accordingly, amaximum pour-point specification is commonly employed in the purchase ofoils intended to be used in cold weather, the pournpoint being thattemperature at which the oil ceases to flow as determined by ASTM methodD97-47.

To produce oils having required low pour-points from stocks of highpour-point, two general procedures are in common use, employed eithersingly or in combination with each other. In one, the oil isrefrigerated to a point where a sufllcient amount of the waxprecipitates and is removed by filtration, thereby lowering thepour-point of the filtrate oil. In the second method, certain additivesare incorporated in the oil which tend to prevent precipitation of thewax. The refrigeration method requires expensive equipment and highoperatnig costs to reduce the temperature of the oil sufiiciently forthe required amount of dewaxing. Such costs make this procedure economiconly with high priced oils and, accordingly, the use of refrigeration isnot commercially practical in the manufacture of diesel oils. Moreover,the pour-point depressant additives commercially available are notgenerally effective in lowering the pour-point of gas oils and dieseloils to the extent required.

The present invention provides a means whereby the pour-point of gasoils may be effectively reduced Without resort to refrigeration.Instead, novel pour depressants, which are highly effective on waxy gasoils and diesel fuels, are made by reacting urea or thiourea withhydrogenated castor oil at about 500 F. The pour depressants of thisinvention are distinguishable from conventional pour depressants used inlube oils since the latter have been found ineffective in waxy gas oils.The accompanying table is illustrative of this advantageous feature.

The term diesel fuel as used herein denotes a fuel suitable for use inhigh speed diesel engines and composed primarily of gas oil. This is incontrast to heavier hydrocarbon fuels designed for use in low speeddiesel engines. The term gas oil is used, as commonly employed by thepetroleum art, to denote distillate oils having boiling ranges betweenabout 350 F. and 750 F.

The order of addition of the reactants to form the pourdepressantmaterials is important. It is imperative that the urea should not beheated up to 500 F. and the hydrogenated castor oil then added becauseurea undergoes self-condensation when heated to form biuret or cyanicacid which polymerizes to polycyanic acid. This eliminates urea fromlater reaction with the hydrogenated castor oil. Alternatively, urea andhydrogenated castor oil may be heated up together to form the pourdepressant reaction products, or, the hydrogenated castor oil may beheated alone to the proper reaction temperature then with the additionof urea the heating continued to maintain this temperature. To avoid anypossibility of urea self-condensations, it is suggested that first thehydrogenated castor oil be heated and then the urea added in anappropriate amount.

While the reaction between hydrogenated castor oil and urea is presumedto occur between the NH groups of urea and the alcoholic OH groups ofthe hydrogenated castor oil requiring a mole ratio of 3 moles of urea to2 moles of hydrogenated castor oil, effective pour depressants can beproduced by Varying the amounts of reactants over fairly wide limits.For example, reactions involving 0.3 mole of urea and 2 moles ofhydrogenated castor oil will yield satisfactory products as is alsofound with reactions with 15 moles of urea and 2 moles of hydrogenatedcastor oil.

Similarly, the temperature of reaction may vary over the range of 350 F.to 600 F. Effective pour depressants can be made by heating the reactionmass for about one hour at 350 F, then increasing the temperature to 600F. and finally allowing the reactants to cool. While the preferred timeand temperature for the reaction is one hour at 500 F, it is possible toproduce an acceptable material after heating for one-half hour at 350 F.Moreover, a suitable product can be made by heating the reactants to 600F. for one-half hour. However, above 600" F. the reaction mixture isprone to catch on fire as well as to form carbon deposits on the sidesof the reaction vessel. Furthermore, prolonged heating, e.g. 8 hours at500 F., decreases the effectiveness of the pour depressant qualities ofthe additive although this by weight concentration thereof is dissolvedin +50 F. pour point gas oil. The pour point of the gas oil is found tobe 15 F.

While the foregoing examples indicate that wide ranges treatment doesnot destroy these qualities completely. in reaction times andtemperatures as well as varying When the reactants are heated togetherbeyond 300 Proportions of reactants result in high q y P011r F. thereaction results in the evolution of gases. At 500 Pressaht mfltefiels,the accompanying table Shows the F. the evolution of gases is vigorousand subsides after applicability of the Products of the invention inreducabout minutes of continued heating. The resulting g the P 'P of gasOils derived from Various enldesreaction mass comprises two phases. Thelower phase is 10 I11 each case illustrating the Present invention themole a white lumpy olid and the upper Phase i a bil ratio of urea tohydrogenated castor oil is 3:2 while the liquid which upon coolingbecomes a soft wax-like matetime and temperature of remit-i011 is 1110111 at 'r rial. The upper phase constitutes the pour depressant ofthe llfea being added after reaction temperature is the presentinvention, and, it may be separated from the reachedlower phase byfiltration while maintaining a suitably 16 It Will be pp from anexamination of the table high temperature, or, by de t ti that theproduct of the invention is a very effective pour The following examplesare ff r d f r th purpose f point depressant and that the inventionsolves a problem illustrating applications of the present invention inspenot readily Solved y other Commercially available matecificinstances: rials such as, for example, poly methacrylates. Tests in-EXAMPLE I 20 dicate that the pour depressants described herein are ofgeneral appllcatlon to most gas 0115.

1000 parts by weight of hydrogenated castor oil are While a 1% by weightconcentration of reaction prodheated to 500 F. To this are added slowly101 parts by net is recommended for effective use in most gas oils,weight of urea while maintaining the temperature above amounts as low as0.3% by weight have been found to be 450 F. The mixture is heated for 1hour at 500 F. satisfactory. On the other hand the upper limits ofwhereby two layers form. The upper layer constitutadditive concentrationare determined by the solubility ing the pour depressant product isseparated from the of the pour depressant material in the stocks used.lower layer by decantationand then cooled. Upon dis- While in theforegoing there are described the presolving a 1% by weightconcentration of the decanted ferred embodiments of the invention whichhave been product in +50 F. pour point gas oil it is founded that foundin practice to give satisfactory and reliable results, the pour point isreduced to 15 F. it is to be understood that the same is susceptible ofmod- EXAMPLE II ification in various particulars without departing fromthe spirit or scope of the invention or sacrificing any of 1000 parts byweight of hydrogenated castor oil are its advantages.

Table Crude 011 Source Waxy" Kuwait Arabian Venture Ventura Ventura WaxContent of Gas Oil Fraction, Wt. Percent. 2. 8 2. 9 4. 8 5. 5 5. 5 5. 5Pour Point, F +25 +25 +50 '+50 Pour Depressant A1 A! A1 A1 B 03Concentration, Wt. Percent 1. 0 l 0 1.0 0. 3 1.0 1. 0 Pour Point ofBlend, F -10 0 -5 -10 +50 +50 Pour Point Depression, F. 50 25 30 0 0 Arepresents the hydrogenated castor oil-urea reaction product of theinvention. B represents a commercial product of the poly methacrylatetype. (3 represents a second commercial product of the poly methacrylatetype.

treated as in Example I except that 10.1 parts by weight of urea areused. A 1% by weight concentration of the decanted product in +40 F.pour point gas oil reduces the pour point to 20 F.

EXAMPLE III 1000 parts by weight of hydrogenated castor oil are treatedas in Example I except that 500 parts by weight of urea are used. A 1%by weight concentration of the decanted product in +40 F. pour point gasoil reduces the pour point to 20 F.

EXAMPLE IV 1000 parts by weight of hydrogenated castor oil and 101 partsby weight of urea are heated to 350 F. and

EXAMPLE V 1000 parts by weight of hydrogenated castor oil and 128 partsby weight of thiourea are heated together at "500 F. for 1 hour wherebythe pour depressant material forms as an upper layer which is decantedfrom the lower layer. The decanted product is then cooled and a 1% Iclaim:

1. A process for forming an oil 'soluble reaction product suit-able foruse as an additive with which to lower below zero Fahrenheit the pourpoint of a waxy gas oil having a boiling range between 350 F. and 750 F.without the need for using subatmospheric pressures, which comprisescontacting hydrogenated castor oil with a compound selected from thegroup consisting of urea and thiourea from about one-half to three hoursat a temperature of from about 350 F. to about 600 F., tsaid compoundbeing added in a ratio from 0.3 mol to 15 mols per two mols of thehydrogenated castor oil, whereby a reaction product is formed as theupper layer in a reaction mixture, and separating said reaction prodnotfrom said mixture.

2. A process as in claim 1 wherein the hydrogenated castor oil isreacted with urea for about one hour at about 500 F.

3. The process of claim 1 in which the castor oil and the said compoundare heated together, and the approximate time of reaction andtemperature is about an hour at 500 F.

4. The process of claim 1 in which the castor oil is first heated toabout 500 F., the compound is urea, the urea is added while maintainingthe temperature above 450 F., the mixture is then heated at about 500 F,for

6. As a new composition of matter suitable for use 10 9,

as a pour point depressant in waxy hydrocarbon gas oils, the oil-solublereaction product prepared by the process of claim 1.

7. A mineral oil composition comprising a waxy gas oil having a boilingrange between 350 and 750 F. in major amount based on the weight ofthecomposition and in excess of 3% by weight, sufficient to depress thepour point of said composition to below zero F., of the oil-solublereaction product prepared by the process of claim 1.

References Cited in the tile of this patent UNITED STATES PATENTS2,599,736 Adelson et a1. June 10, 1952 Adelson et a1. June 10, 19522,657,984 Braithwaite Nov. 3, 1953 OTHER REFERENCES Organic Chemistry,by Karrer, Elsevier Pub. Co.,

15 1947, 3d ed., page 222.

1. A PROCESS FOR FORMING AN OIL-SOLUBLE REACTION PRODUCT SUITABLE FORUSE AS AN ADDITIVE WITH WHICH TO LOWER BELOW ZERO FAHRENHEIT THE POURPOINT OF A WAXY GAS OIL HAVING A BOILING RANGE BETWEEN 350*F. AND 750*F. WITHOUT THE NEED FOR USING SUBATMOSPHERIC PRESSURES, WHICH COMPRISESCONTACTING HYDROGENATED CASTOR OIL WITH A COMPOUND SELECTED FROM THEGROUP CONSISTING OF UREA AND THIOUREA FROM ABOUT ONE-HALF TO THREE HOURSAT A TEMPERATURE OF FROM ABOUT 350* F. TO ABOUT 600* F., SAID COMPOUNDBEING ADDED IN A RATIO FROM 0.3 MOL TO 15 MOLS PER TWO MOLS OF THEHYDROGENATED CASTOR OIL, WHEREBY A REACTION PRODUCTS IS FORMED AS THEUPPER LAYER IN A REACTION MIXTURE, AND SEPARATING SAID REACTION PRODUCTFROM SAID MIXTURE.